THANKS to an unlikely confluence of history and genetics - the fact that he is African-American and president - Barack Obama has a unique opportunity to reshape the debate over one of the most contentious issues of America's racial legacy: reparations, the idea that the descendants of American slaves should receive compensation for their ancestors' unpaid labor and bondage.

There are many thorny issues to resolve before we can arrive at a judicious (if symbolic) gesture to match such a sustained, heinous crime. Perhaps the most vexing is how to parcel out blame to those directly involved in the capture and sale of human beings for immense economic gain.

While we are all familiar with the role played by the United States and the European colonial powers like Britain, France, Holland, Portugal and Spain, there is very little discussion of the role Africans themselves played. And that role, it turns out, was a considerable one, especially for the slave-trading kingdoms of western and central Africa. These included the Akan of the kingdom of Asante in what is now Ghana, the Fon of Dahomey (now Benin), the Mbundu of Ndongo in modern Angola and the Kongo of today's Congo, among several others.